Pressure, absolute vessel design

Internal pressure P (absolute) at failure. (A typical BLEVE is caused by a fire whose heat raises vessel pressure and reduces its wall strength. Safety-valve design allows actual pressure to rise to a value 1.21 times the safety valveopening pressure.)... 

The design overpressure of the vessel is 1.92 MPa, and the test pressure is 25% higher. Therefore, the absolute internal pressure p, is... 

Figure 2-47. Acceptable pressure losses between the vacuum vessel and the vacuum pump. Note reference sections on figure to system diagram to illustrate the sectional type hook-ups for connecting lines. Use 60% of the pressure loss read as acceptable loss for the system from process to vacuum pump, for initial estimate. P = pressure drop (torr) of line in question Po = operating pressure of vacuum process equipment, absolute, torr. By permission, Ryans, J. L. and Roper, D. L., Process Vacuum System Design Operation, McGraw-Hill Book Co., Inc., 1986 [18].

Example 7.8. The fill line in a liquid nitrogen storage vessel is constructed of a 50-mm nominal stainless-steel pipe. Determine the minimum thickness of the line, the schedule number that should be specified for the line, and the heat leak down the pipe to the inner vessel when one end of the 3-m line is at 300 K and the other end is at 77.8 K. The design pressure for the inner vessel is 800 kPa absolute. 

A spherical cryogenic container with a nominal capacity of 2000 m and a 10% ullage volume is used to store liquid hydrogen. The inner vessel is constructed of 304 stainless steel with spot examined butt joints and complete penetration welds. The outer shell, which has an inner diameter that is 1.25 m larger than the outer diameter of the inner shell, is constructed of carbon steel, SA-285, grade C. If the design pressure is 500 kPa absolute, determine the minimum thicknesses that are required for the inner and outer shells, respectively. 

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